1. Field of the Invention
The present invention relates to a method for transferring devices. More particularly, this invention can be applied in transferring the devices to a flexible substrate.
2. Description of the Prior Art
As the flat panel display is developed toward large area, the characteristics of lightness, thinness, and flexibility are another trends. The main trend of the development is to use a plastic substrate in place of a glass substrate. Nowadays, the flat panel display is produced on the glass panel for the advantages of great area and mass production, but the substrate has been changed into the plastic substrate when the advantages of lightness, thinness and flexibility are required. However, the process temperature of the thin film transistor liquid crystal display (TFT-LCD) fabrication is 300˜400° C., so the plastic substrate is not applicable to TFT-LCD fabrication. Thus, many alternative methods are developed, particularly, the method of reducing the process temperature and transferring devices. However, the method for reducing the process temperature will affect the characteristic of the device and cause the problems of bad adhesion, lithography over-focus, stress, static electricity and so on. Therefore, the method of transferring devices is more feasible.
Please refer to FIGS. 1A–1F. FIGS. 1A–1F are perspective diagrams showing steps of a prior art transfer technology disclosed in U.S. Pat. No. 6,127,199. In FIG. 1A, a light absorption layer 12 is formed on the substrate 10. In FIG. 1B, a device layer 14 is formed on the light absorption layer 12. The detailed description for the device 15 in the device layer 14 will not be described because it is not crucial in this technology. Please refer to FIG. 1C, an adhesive layer 16 is used to pasting the transferred substrate 18 to the device layer 14. As shown in FIG. 1D, The laser light is irradiated through the substrate and the light absorption layer so as to separate the substrate from the light absorption layer. Please refer to FIG. 1E. Practically, the light absorption layer 12 may be removed together with the substrate 10. If not, the methods of washing, etching and polishing can be used for removing the light absorption layer 12, as FIG. 1F shown. This is a well-known prior art. However, the drawback is to precisely control the energy of the laser light for preventing the thin-film LCD device from damage.
Please refer to FIGS. 2A–2F. FIGS. 2A–2F are perspective diagrams showing steps of a prior art transfer technology of devices disclosed in U.S. Pat. No. 6,232,136. As shown in FIG. 2A, an upper and a lower oxidization layers 34, 32 are positioned on the substrate 30. Besides, an isolation layer 36 is positioned on the upper oxidization layer 34. Then, a thin film 38 is positioned on the isolation layer 36, and the devices 40 are formed on the thin film 38. FIG. 2B shows the step for opening a hole 42 on the isolation layer 36 and the upper oxidization layer 34. Then, as shown in FIG. 2C, the resin 48 is filled in the opening hole 42, after the filling, via holes 46 are formed on the isolation layer 36. Please refer to FIG. 2D. With the support of the resin 48, the upper oxidization layer 34 is removed by lateral etching process so as to form the structure with a blank layer 50. Thereafter, with the support of the resin 48, the reserved resin 82 and the removed resin 84 are form. Please refer to FIG. 2E. A transition substrate 80 is further positioned on the reserved resin 82 and the removed resin 84. Finally, please refer to FIG. 2F. The removed resin 84 connected to the resin 48 is removed together with a part of the isolation layer 36 so as to complete the process of the transfer.
The above is the detailed description of the two prior art technologies. However, in order to achieve the object of transferring the devices, the precise controlling for the energy is required and the complicated process has to be handled. Therefore, the practical application is faulty and other technology has to be further developed and applied so as to accomplish the devices transfer.